This invention relates to methods for treating or preventing the skin photoaging process and skin cancer.
Photoaging, or premature aging, is a process in which the skin changes in appearance as a result of repeated exposure to sunlight. Typically, photoaging occurs in areas of habitual exposure, such as the scalp, face, ears, neck, chest, forearms, and hands. The changes associated with photoaging include elastosis, atrophy, wrinkling, vascular changes (diffuse erythema, ecchymoses, and telangiectasias), pigmentary changes (lentigines, freckles, and areas of hypo- and hyper-pigmentation), and the development of seborrheic keratosis, actinic keratosis, comedones, and cysts. By contrast, chronologically-based aging of sun-protected skin results in skin that has thinned and lost elasticity, but which has otherwise remained smooth and unblemished.
Exposure to sunlight causes DNA mutagenesis, enzyme inactivation, inhibition of cell division, and cell death, therefore increasing the risk of developing skin cancers including basal cell carcinomas, squamous cell carcinomas, and malignant melanomas. The principle mediator of the carcinogenesis in the skin involves the formation of pyrimidine dimers between thymidine-thymidine, cytosine-thymidine, and cytosine-cytosine nucleotide pairs.
The ultraviolet (UV) component of sunlight, especially the middle UV (called UVA/B, 290-400 nm wavelength), is thought to be the principal causative agent which induces the photoaging and carcinogenic effects of sunlight in skin. Oxygen free radicals, which increase upon UV exposure, have been proposed to be mediators of the photoaging and carcinogenic effects of UV light (Reiger, Cosmetics and Toiletries 108: 43-56, 1993; Southorn PA, Free radicals in medicine. 1. Chemical nature and biologic reactions. Mayo Clin. Proc. 63: 391, 1988). Free radicals are highly reactive molecules with unpaired electrons in the outer orbital. While free radicals perform some beneficial tasks, such as participating in the destruction of microorganisms and cancer cells, excessive levels can lead to DNA mutagenesis and damage to cellular structure (Southorn, supra).
Matrix metalloproteases (MMPs), which degrade collagens, elastins, and other proteins in the connective tissue network, are also proposed to be mediators of photoaging. Upon UV exposure, the transcription factors AP-1 and NF-xcexaB are increased, which, in turn, increase expression of MMPs, such as collagenase, 92 kD gelatinase, and stromelysin-1 (Fisher et al., N. Engl. J. Med. 337: 1419-1428, 1997).
Based on the above proposed mechanisms, the use of antioxidants to reduce oxygen free radicals in the skin and the use of compounds that inhibit the components of the MMP pathway have been disclosed as treatments for UV-based skin cancer and photoaging (Southorn, supra; Fisher et al., N. Engl. J. Med. 337: 1419-1423, 1997; Voorhees et al., U.S. Pat. No. 5,837,224). Given that these treatments have resulted in only marginal success, there is a clear need for the identification of new targets in the photoaging and carcinogenic processes and the development of drugs that affect these new targets.
The kallikrein-kinin pathway includes kallikreins and bradykinins. Kallikreins are serine proteases, and are divided into two principal groups: tissue kallikreins (EC number 3.4.21.35) and plasma kallikrein (EC number 3.4.21.34).
Plasma kallikrein has a molecular weight of about 100 kD, circulates in the blood in a precursor form called prekallikrein, and is principally involved in the activation of the blood clotting and complement enzyme cascades.
Tissue kallikreins, otherwise known as glandular or organ kallikreins, are glycoproteins with a molecular weight ranging from 27-40 kD. They have been isolated from various tissue and body fluids including saliva, intestine, lung, brain, plasma, and the sweat glands of the skin. Their substrates include procollagenase, kininogen, proinsulin, prorenin, BAM 22P atrial natriuretic factor, low density lipoprotein, atriopeptigen, and tissue plasminogen activator.
The major effectors of kallikrein activation are bradykinin, Lys-bradykinin (kallidin), and Met-Lys bradykinin, which are produced by kallikrein cleavage of kininogen. Kininogen is a hepatic-derived protein which circulates in the blood in a low molecular weight form and a high molecular weight form. Tissue kallikreins are relatively specific for cleavage of the low molecular weight form; plasma kallikrein has greater specificity for the high molecular weight form.
Bradykinins are autocoids, that is, they are hormones that are synthesized locally and act locally. This local effect is due to the short half-life (less than 30 seconds) of bradykinins and their almost complete destruction in the first pass through the pulmonary circulation (Ferreira and Vane, Chemotherap. 30: 317, 1967). In addition to playing a role in inflammation, bradykinins also lower blood pressure, participate in blood clotting and complement reactions, mediate rhinitis, and cause pain.
The major effects induced by bradykinins are vasodilation, increased vascular permeability, and inflammation. The inflammatory process involves the infiltration of neutrophils, macrophages, lymphocytes, mast cells, and other lamina proprira cells, including fibroblasts, to the site of inflammation. These inflammatory cells then function to synthesize and release several arachidonic acid-related mediators of inflammation, such as prostaglandins, leukotrienes, and thromboxanes.
The invention features a method of treating or preventing photoaging of the skin. The method includes administering a compound to a patient that inhibits one or more components of the kallikrein-kinin pathway in an amount sufficient to reduce or prevent a symptom of photoaging. The symptom of photoaging is mediated by activation of the pathway, and can be caused by inflammation, vasodilation, or increased vascular permeability in the skin. Examples of symptoms of photoaging that can be reduced or prevented by the method of the invention include elastosis, atrophy, wrinkling, vascular changes, pigmentary changes, seborrheic keratosis, actinic keratosis, comedones, and cysts.
The compound can be administered systemically or topically. The compound can be in a liposomal formulation and is preferably administered immediately prior to, or during, photoexposure. Preferably, the compound is a nonsteroidal antiinflammatory drug (NSAID), or inhibits bradykinin activity, preferably, it inhibits bradykinin activation of the BK2 receptor, or inhibits kallikrein activity, more preferably, tissue kallikrein activity.
Another aspect of the invention features a method of assessing whether an inhibitor of the kallikrein-kinin pathway is an effective compound for treating or preventing photoaging. The method includes contacting the compound with skin before, during, or after photo or UV exposure, and measuring whether the compound significantly reduces a kallikrein-kinin pathway related change in the skin.
The invention also includes a method of treating or preventing skin cancer. The method includes administering a compound to a patient that inhibits one or more components of the kallikrein-kinin pathway in an amount sufficient to reduce or prevent a symptom of skin cancer. The symptom of skin cancer is mediated by activation of the pathway, and can be caused by inflammation, vasodilation, increased vascular permeability, and generation of nitric oxide and oxygen free radicals in the skin. Examples of symptoms of skin cancer that can be reduced or prevented by the method of the invention include precancerous or cancerous changes to skin morphology, actinic keratosis, basal cell carcinomas, squamous cell carcinomas, and malignant melanoma.
The compound can be administered systemically or topically, preferably, the compound is in a liposomal formulation and is administered immediately prior to, or during, photoexposure. Preferably, the compound is a nonsteroidal anti-inflammatory drug (NSAID), or inhibits bradykinin activity, more preferably, the compound inhibits bradykinin activation of the BK2 receptor, or inhibits kallikrein activity, more preferably, tissue kallikrein activity.
Another aspect of the invention features a method of assessing whether an inhibitor of the kallikrein-kinin pathway is an effective compound for treating or preventing skin cancer. The method includes contacting the compound with skin before, during, or after photo or UV exposure, and measuring whether the compound significantly reduces a kallikrein-kinin pathway related change in the skin. The change in the skin can be increased oxygen free radicals or increased DNA mutagenesis.
By xe2x80x9ca kallikreinxe2x80x9d is meant a tissue kallikrein or plasma kallikrein.
By xe2x80x9ca bradykininxe2x80x9d is meant bradykinin, Lys-bradykinin (kallidin), or Met-Lys bradykinin.
By xe2x80x9can enzyme in the arachidonic acid metabolic pathwayxe2x80x9d is meant an enzyme, such as cyclooxygenase, lipoxygenase, or prostaglandin synthetase, that plays a role in converting arachidonic acid to various products such as prostaglandins, leukotrienes, and thromboxanes.
By xe2x80x9ca component of the kallikrein-kinin pathwayxe2x80x9d is meant a kallikrein, a bradykinin, or an enzyme in the arachidonic acid metabolic pathway that plays a role in the activation of the kallikrein-kinin pathway and causes the onset of a symptom of photoaging or skin cancer by mediating a kallikrein-kinin pathway-related change in the skin.
By xe2x80x9can inhibitor of the kallikrein-kinin pathwayxe2x80x9d is meant a compound that inhibits a component of the kallikrein-kinin pathway, such that the activation of the pathway, for example, following exposure to the sun, is reduced. This inhibition results in a reduced occurrence of a symptom of photoaging or skin cancer, or a reduction in a kallikrein-kinin pathway-related change in the skin, following activation of the pathway. The inhibitor either inhibits or antagonizes the enzymatic or hormonal activity of the component or reduces the protein level of the component.
By xe2x80x9ca kallikrein-kinin pathway-related change in the skinxe2x80x9d is meant a change mediated by the activation of the kallikrein-kinin pathway, for example, inflammation, infiltration of inflammatory cells, vasodilation, increased vascular permeability, increased oxygen free radicals, increased nitric oxide, increased DNA mutagenesis (for example, pyrimidine dimerization), increased matrix metalloproteases (MMPs), increased deposition of elastin material, reduced types I and III collagen precursors, or an increased ratio of type III to type I collagen.
By xe2x80x9ca symptom of photoagingxe2x80x9d is meant one of the following symptoms that occur in response to habitual exposure of the skin to sunlight: elastosis (an increased coarseness and yellowing discoloration of the skin); atrophy (thin and easily torn skin); wrinkling; vascular changes, for example, diffuse erythema, ecchymoses, and telangiectasias (dilation due to thinning of vessel walls); pigmentary changes, for example, lentigines (liver spots), freckles, and areas of hypo- and hyper-pigmentation; and the development of seborrheic keratosis, actinic keratosis, comedones (obstruction of ducts of the skin), and cysts.
By xe2x80x9ca symptom of skin cancerxe2x80x9d is meant one of the following symptoms that occur in response to habitual exposure of the skin to sunlight: the appearance of precancerous or cancerous changes to skin morphology, including actinic keratosis, basal cell carcinomas, squamous cell carcinomas, and malignant melanoma.
By xe2x80x9ctreating or preventing photoagingxe2x80x9d or xe2x80x9ctreating or preventing skin cancerxe2x80x9d is meant producing a detectable reduction in a symptom of photoaging or skin cancer, respectively, or preventing the occurrence or exacerbation of a symptom under conditions known to induce such symptoms, such as sun exposure.
By xe2x80x9ca kallikrein inhibitorxe2x80x9d is meant a compound which causes a reduction of kallikrein enzymatic activity or protein level and includes, but is not limited to, serpin, C1 inhibitor, xcex12 macroglobulin, antithrombin-III, ecotin, and broad spectrum Kunitz-type serine protease inhibitors (such as aprotinin and its variants), an antibody to a kallikrein, diisopropylfluorophosphate, pefablock (Interchim), and other exemplary inhibitors listed in U.S. Pat. Nos. 5,786,328, 5,770,568, or 5,464,820.
By xe2x80x9ca bradykinin inhibitorxe2x80x9d is meant a compound that reduces the activity or level of the autocoid. Preferred inhibitors are icatibant and CP0597 (Cortech). Other exemplary inhibitors include, but are not limited to, those listed in U.S. Pat. Nos. 5,700,779; 5,750,506; 5,610,140; 5,863,899, 5,849,863; 5,843,900; 5,834,431, 5,635,593; 5,416,191; 5,620,958; 5,563,162; 5,750,669; 5,574,042; 4,801,613, 5,578,601, 4,693,993, WO 96/13485; WO 96/40639; WO 97/07115; WO 97/11069; EP 773,932 A1; EP 596,406 A1; EP 596,406 B1; EP 787,131 A1; EP 861,243 A1; EP 807,105 A1; EP 622,361 A1; U.S. Pat. No. 5,849,312; U.S. Pat. No. 5,212,182; EP 578,521; EP 564,972; EP 548,825; EP 552,106; FR 2,686,343; WO 93/11789; and the indirect bradykinin inhibitors listed in U.S. Pat. No. 4,801,613. Preferred inhibitors are specific for the BK2 receptor, such as icatibant and CP0597.
By xe2x80x9can inhibitor of the arachidonic acid metabolic pathwayxe2x80x9d is meant a compound that reduces the activity or level of cyclooxygenase, lipoxygenase, prostaglandin synthetase, or another enzyme that plays a role in converting arachidonic acid to its various metabolic products. Examples of such inhibitors include, but are not limited to, nonsteroidal anti-inflammatory drugs, salicylates, and cyclooxygenase inhibitors.
By xe2x80x9ca nonsteroidal anti-inflammatory drug (NSAID)xe2x80x9d is meant a compound that reduces inflammation. Preferred NSAIDs include, but are not limited to, naproxen, nabumetone, diclofenac, sulindac, oxaprosin, diflunisal, bromfenac, aspirin, piroxicam, indomethacin, etodolac, ibuprofen, fenoprofen, flurbiprofen, ketorolac, nimesulide, NS-398, ketoprofen, trisalicylates, acetominophen, oxaprosin, salsalate, rofecoxib, and celecoxib.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.